Degradation And Release Of Electrospun Poly ((L-lactide) Membranes Under Dynamic/Static Conditions

As we all know, human body is under a dynamic load environment rather than in a static environment. It's necessary to imitate the degradation of the scaffold material under a dynamic load. Besides, it is a simple, direct and effective research method to load drug into the electrospun membrane directly and imitate the release under a dynamic load. In this research, electrospun PLLA, PLLA/BTEAC (benzyl triethyl ammonium chloride), PLLA/Dex (dexamethasone) membranes were prepared by electrospinning, and the effects of Proteinase K and cyclic tensile load (dynamic condition) on fiber's degradation and drug-release were investigated.The effect of Proteinase K, cyclic tensile load and morphology of the electrospun membrane on fiber's degradation were discussed. The results showed that the average fiber diameter reduce from 389.9±10.8nm to 262±9.4nm and the fiber morphology improved when BTEAC was introduced in electrospining. Degradation electrospining PLLA and PLLA/BTEAC membrane under dynamic/static conditions were carried out in Tris-HCl/Proteinase K and Tris-HCl buffer solution, respectively. The results showed that Proteinase K affect the membrane's degradation mostly while tensile load can also accelerate the degradation of the membrane. Weight loss of electrospun membrane was 39.09% after 10 hours of degradation in Tris-HCl/Proteinase K buffer solution. Since lactic acid molecules were released during the degradation process, pH value of the buffer solution lowered significantly. The introduction of BTEAC can change membrane's Xc significantly and the Xc increased in different degree after degradation. SEM results showed that the fibers'morphology changed obviously, and become large deformation, fracture as well as the more rougher surface. The viscosity average molecular weight changed slightly after degradation.The effect of Proteinase K and cyclic tensile load on fiber's drug-release was also discussed in this research. The results showed that the introduction of 1% Dex can improve the fiber morphology and the average fiber diameter reduce from 389.9±10.8nm to 257.4±8.6nm. The dynamic/static contrast release experiments of PLLA/Dex electrospun membrane were carried out in Tris-HCl/Proteinase K and Tris-HCl buffer solution, respectively. The results showed that the drug released almost linearly within 10 hours, and the release amount under dynamic and static condition reached 57.67±3.01% and 54.43±1.45%, respectively in Tris-HCl/Proteinase K buffer solution. In Tris-HCl buffer solution, release under dynamic condition follow the same way, the release amount reached 48.06±3.21% after 10 hours degradation. Release under static condition was divided into two stages, namely, drug burst release stage in first 0-4 hours and smooth release stage in later 4-10 hours, and the release amount reached 29.43±1.56% at the end of the research. The introduction of Dex can change membrane's crystallinity significantly and the Xc increased in different degree after release.